1. Field of the Invention
The present invention generally relates to optical transmission apparatuses, and particularly relates to an optical transmission apparatus using an optical module that is pluggable to the optical transmission apparatus.
2. Description of the Related Art
Optical transceivers (optical modules) used in optical transmission apparatuses provided for backbone networks as typified by SONET, SDH, WDM, etc., are developed by makers and manufacturers using their own designs and interfaces, and thus do not possess universal applicability. Against this background, the MSA (Multi-Source Agreement) has been established as an industry standard for the optical module industry for the purpose of achieving cost advantage and revitalizing the optical module industry. This has resulted in the spread of optical modules having universal applicability based on standardized design and interface. Among such standardized optical modules (MSA modules), those with pluggable structure such as SFP (Small Form Factor Pluggable) and XFP (10 Gigabit Small Form Factor Pluggable) have been becoming mainstream.
As the market penetration of such pluggable modules is made, communication carriers who utilize optical transmission apparatuses to provide services are now demanding the use of optical modules purchased through their own purchase channels for the benefit of cost advantage, and are also demanding the reduction of repair cost by making it possible to replace only a pluggable module upon failure. Because of this, the optical transmission apparatuses employing standardized pluggable optical modules are now required to have such a structure as to allow optical modules to be freely replaced.
When pluggable optical modules are employed for optical transmission modules, the main issue is how to keep balance between the reliability of the apparatuses and the convenience of the pluggable optical modules (high availability, easy maintenance, low cost, and so on). In the following, three examples of the related-art usage of a pluggable optical module will be described.
FIG. 1A is a drawing showing a first usage type. A pluggable optical module 1 is fixedly mounted in an optical transmission apparatus 2. In this configuration, only those which have passed the test by the manufacturers at the time of shipment from factory are mounted. This can avoid use of poor-quality products, thereby making it possible to ensure the reliability of the apparatuses.
FIG. 1B is a drawing showing a second usage type. A pluggable optical module 3 is freely pluggable to an optical transmission apparatus 4, which provides for easy maintenance at the time of failure or the like. Also, clients can make their own choice to select inexpensive optical modules, so that the manufacturers can provide cost advantage to the clients.
FIG. 1C is a drawing showing a third usage type. A pluggable optical module 5 has such a structure as to be pluggable to an optical transmission apparatus 6. A CPU 7 of the optical transmission apparatus 6 checks the optical module by comparing the module code read from the optical module 5 via a DDM (Digital Diagnostics Monitor) interface 8 with the module code of an operable optical module stored in a memory 9. If a module having a wrong code is mounted, an alarm is issued to a monitoring control apparatus so as to prevent the use of the optical module 5.
Patent Document 1 discloses transmitting a membership number read from a membership card by a hall-installed apparatus to a management computer, which reads a membership classification flag stored in memory in response to the membership number for transmission to the hall-installed apparatus, so that the hall-installed apparatus displays the membership class of the member as indicated by the membership classification flag.
Patent Document 1 Japanese Patent Application Publication No. 10-156022
The first usage type cannot make use of the convenience of a pluggable optical module such as the fact that it is pluggable, and, also, cannot allow a client to use an optical module that the client obtained through his/her own channel.
The second usage type raises concern that a pluggable optical module not suitable to the apparatus or a poor-quality module may be used. In the worst case, there is a possibility of having a situation in which the communication channel fails while it is used. That is, the reliability of the apparatus may not be guaranteed.
The third usage type allows only exactly the same product as specified by the manufacture to be used when replacing the pluggable optical module 5 upon failure of the pluggable optical module 5, and does not allow the use of a pluggable optical module having the same characteristics if it is not the type as specified. Further, it is not possible for a client (communication carrier) using the apparatus to make its own choice to select an inexpensive pluggable optical module. That is, no cost merit is provided to clients.
Further, if an inexpensive pluggable optical module that is not fully supported by the manufacture is chosen, there is a need to check, before putting this pluggable optical module into operation, whether this module properly operates in the optical transmission apparatus and whether this module has sufficient characteristics for operation of the communication channel. A test that is currently conducted by the manufacturers for the purpose of checking a pluggable optical module for certification is performed by assuming the worst conditions (in terms of ambient temperature, transmission distance, etc.) in which the pluggable optical module is operated. Only those which passed this rigorous test are certified. This is the same when a client makes its own choice to select a pluggable optical module. That is, there are needs to determine product specifications by assuming the worst conditions for operation, to prepare a dedicated measurement device to conduct an optical-characteristic test, a transmission test, etc, and to actually perform various test items. In this manner, a large number of process steps are required in order to select a pluggable optical module.
In reality, however, the conditions of use, transmission distance, etc., differ from communication line to communication line, and not all the optical modules are used in the worst conditions. Conducting tests by determining product specifications based on the worst conditions serves to narrow the range of choices of an pluggable optical module to be used. Further, a large number of optical module venders rigorously develop and update new pluggable optical modules to sell inexpensive optical modules. Against this background, the reduction of a number of process steps for product certification is an important issue.
Accordingly, there is a need for an optical transmission apparatus that can clearly specify the range of product guarantee while offering ease of maintenance and cost advantage, and that can widen the range of choices of pluggable optical modules to be used.